Toy inflatable balloons have traditionally been made of rubber. Balloons made of Mylar and other sheet materials, usually metalized, have been introduced which are less pervious to gas losses and can retain helium, for example, for several days. Sealing the openings through which the ballons are inflated has, however, presented a problem.
One attempt at sealing balloons of sheet material has been to twist the ends or neck portions thereof following inflation and tying the twisted ends with a string. This approach has not, however, proved satisfactory since excessive losses of gas have taken place through the twisted and tied ends.
Spring clips have also been used in an effort to seal off the open ends of foil-type balloons. These clips are typically applied to the twisted ends of the balloons to pinch or squeeze the twisted ends thereby to halt escape of gas. However, irrespective of the biasing forces applied to the twisted ends by the spring clips, minute channels have remained through which gases can gradually escape.
A number of plugs have been proposed for sealing the openings through which film balloons are inflated. Some of these plugs are generally tapered and are intended to be simply forced into suitable valve openings following inflation. Reliance on force fits, however, have not proved satisfactory because of the difficulty of manufacturing processes in providing sufficiently close tolerances. Other plugs have been more elaborate. In all cases, however, such plugs have tended to be too complex, too expensive and too heavy to be practical.
Another approach has been to heat seal the open ends subsequent to inflation. While such sealing has reduced the amount of gas leakage, it has been inconvenient to use and has required heat sealing equipment which must be connected to power lines thereby reducing its mobility. Also, the heat seals produced have not been consistently satisfactory, particulary when made by inexperienced operators.